Someone who is so bipolar, that everything they say has a different emotion to it, so you never know what to expect.
Also a wide-range of emotions in a short time. This is not considered classy in any way.

Jessica: Hey Justin. How are you?
Justin: I'm having a great day.
Jessica: That's really good.
Justin: NO IT ISN'T I HATE MY LIFE.
Jessica: .......
Justin: JKLOL BAHAHAHAHAH
Jessica: Jeez, stop being so chromatic....